Researchers from the Park Service found two separate litters of mountain lion kittens living in the Santa Susana Mountains north of Los Angeles. The NPS has released videos of the kittens, which the service tagged as part of a study into how mountain lions are affected by human infrastructure in and around Los Angeles.

The lions appear to be reproducing successfully, according to wildlife biologist Jeff Sikich, but the threats will pile up as the kittens age, he told the Los Angeles Times.

“The real challenge comes as these kittens grow older and disperse, especially the males, and have to deal with threats from other mountain lions, road mortality, and the possibility of poisoning from anticoagulant rodenticide,” he said.

One litter has two female kittens born to a mother tagged as P-35. The other litter contains two males and a female, born to mother P-39. Both litters are believed to have the same father, P-38.

About 50 percent of California is considered a potential habitat for mountain lions, which have come a long way in the last century. Considered a threat to animal husbandry because of their habit of picking off livestock, they were declared a “bountied predator” in 1907, with a $20 incentive offered for each one killed. In 1919, the state even hired a pair of full-time hunters, adding trappers and two more hunters to their payroll in subsequent decades.

In the 1960s, as protectionist feeling began to spread among a greater portion of the public, the bounty program ended, and the lions began gaining protections that culminated in a moratorium on hunting them in 1990.

That moratorium, still in effect, has helped the population grow from an estimated 2,000 in the 1970s to between 4,000 and 6,000 at present, according to the California Department of Fish and Game Services. The lions are not considered threatened or endangered in the state, so while there is no season on the big cats, about 60 are legally killed each year with depredation permits, plus others killed for posing a threat to humans or endangered bighorn sheep.

In some parts of California, particularly in towns adjoining rural areas, run-ins with the big cats aren’t uncommon. In February, the San Francisco Chronicle reported that a Department of Fish and Wildlife study had found that of the 107 mountain lions legally killed last year, almost half had traces of cats, dogs, and other domestic animals in their stomachs.

The National Park Service researchers who found the new litters say they identified the father by using GPS tracking data.